Guitar Chord Types
A guitar chord or chord on any instrument is a group of three or more notes played back in quick succession or together. There is also a modern convention of showing a power chord or fifth interval (which has only 2 notes) as a "5" chord. The 3rd is missing from this chord and therefore you cannot tell whether it is a major or minor chord. This is not officially a chord but makes a lot of sense to guitar players who use this kind of "chord" all the time, especially if you play hard rock, grunge, metal etc.
The descriptions of the chord types listed below refer to the music intervals, triads and other stuff which is covered in the music theory section. There is a link to triad chords at the bottom, have a look at this as it helps explain the building blocks of chord and chord theory.
Chords can be separated into these groups:
A major chord contains a root, major third and a perfect fifth and is considered to sound quite upbeat or happy :).
A mnior chord contains a root, minor third and a perfect fifth and is considered to sound quite melancholic or sad :(.
A seventh chord contains a triad with a seventh interval on top. If not specified the seventh will be the 'dominant' seventh, which means a major triad with a minor seventh interval above. A minor seventh chord contains a minor triad with minor seventh interval. A major seventh chord contains a triad with the third being a major third and with a major seventh interval.
A sixth chord contains a triad with a sixth interval on top. If not specified the chord will have a major triad with a major sixth interval above. A minor sixth chord contains a minor triad with minor sixth interval on top.
With a suspended chord, where the third would normally be in a major or minor triad, this is replaced by a perfect fourth or a major second. The fourth is the more commonly used. These chords have a feeling of "suspension" where the sus4 or sus2 wants to resolve to the 3rd of the chord.
A diminished triad uses two minor 3rd intervals stacked on top of each other. For a full diminished add another minor 3rd interval on top. A half-diminished chord is a diminished triad with a major third on top.
slash chords / split chords
Slash chords or split chords are where the lowest note in the chord is not the root note.
Triad means three notes. You may not have used the expression triad or triad chords but these are the basic building blocks of chord theory. There are four different types: major, minor, diminished and augmented.